OK, let's do this. We've got 2531 and 3130 and we're adding them all together.

Step 1: We'll start by adding the digits 1 & 0 in column 1 and get 1.

Step 2: We'll start by adding the digits 3 & 3 in column 2 and get 6.

Step 3: We'll start by adding the digits 5 & 1 in column 3 and get 6.

Step 4: We'll start by adding the digits 2 & 3 in column 4 and get 5.

So, 2531 + 3130 = 5661.

